THE SKATE. 47 



XVI. Place the animal with the ventral side upwards, 

 turn the lobes of the liver forwards so as to 

 expose the remaining abdominal viscera, and 

 without cutting or tearing anything, make out the 

 following points : — 



89. The relations of the various parts of the aUmentary 

 canal: the oesophagus or gullet enters the abdominal 

 cavity through its anterior wall, to the dorsal side of the 

 liver, and almost immediately dilates slightly to form the 

 stomach : this passes to the posterior boundary of the 

 abdomen, becomes narrowed, turns upon itself, and passes 

 forward to about the middle of the cavity, where it forms a 

 thickening — the pylorus — and becomes continuous with the 

 intestine : this is, in its anterior or proximal portion, 

 devoid of the spiral groove mentioned in § 75, and loses 

 it again in its posterior or distal part, shortly before it 

 passes into the dilated cloaca : the anterior smooth 

 portion of the intestine may be called the duodenum, 

 the middle, dilated, spirally-marked portion the colon, 

 and the posterior smooth portion the rectum : to the 

 latter is attached, dorsally, a small conical red body, the 

 rectal gland. 



90. The mode of attachment of the alimentary canal. 

 The posterior part of the oesophagus and anterior part of 

 the stomach are suspended to the dorsal wall of the abdo- 

 minal cavity by a fold of peritoneum, the mesogaster : 

 the rectum is similarly suspended by a second fold, the 

 mesorectum. The greater part of the intestine, on the 

 other hand, is entirely unsuspended, so that there is no 

 mesentery proper. 



91. The fold of peritoneum— gastro-hepatic omen- 

 tum — which passes between the liver and stomach, and is 

 joined near the latter by a similar but much longer fold, the 



